Nonpaged Pool is over the warning threshold

[This topic is intended to address a specific issue called out by the Exchange Server Analyzer Tool. You should apply it only to systems that have had the Exchange Server Analyzer Tool run against them and are experiencing that specific issue. The Exchange Server Analyzer Tool, available as a free download, remotely collects configuration data from each server in the topology and automatically analyzes the data. The resulting report details important configuration issues, potential problems, and nondefault product settings. By following these recommendations, you can achieve better performance, scalability, reliability, and uptime. For more information about the tool or to download the latest versions, see "Microsoft Exchange Analyzers" at]  

Topic Last Modified: 2009-09-01

The Microsoft® Exchange Server Analyzer Tool queries the Win32_PerfRawData_PerfOS_Memory Microsoft Windows® Management Instrumentation (WMI) class to determine the current value for the PoolNonpagedBytes key. The actions taken by the Exchange Server Analyzer depends on the underlying operating system, the presence or absence of the /3GB switch in the Windows Boot.ini file, and the discovered value for this key.

The following table displays the matrix of evaluations used by the Exchange Server Analyzer to determine whether this value is out-of-bounds for a specified Exchange server. If the conditions in the following table are matched, a warning is displayed.

Operating System Boot.ini Setting Current Non-Paged Pool is

Microsoft Windows 2000 Advanced Server


100 MB or more

Microsoft Windows 2000 Server or Advanced Server


200 MB or more

Microsoft Windows Server™ 2003


100 MB or more

Microsoft Windows Server 2003


200 MB or more

The PoolNonpagedBytes key value is the size, in bytes, of the kernel memory non-paged pool. This is an area of physical system memory for objects that cannot be written to disk even when they are not being used. This value for this key is the last observed value. On a healthy Exchange server, unless a backup or restore is occurring, there should be no more than 85 MB of non-paged pool memory being used.

In Windows 2000 Server and Windows 2000 Advanced Server, the maximum value for non-paged pool memory is 256 MB. Because you cannot increase the limit for non-paged pool memory beyond the values listed above, this condition should be corrected as soon as possible. Regardless of the operating system in use or the presence or absence of the /3GB switch, only so much non-paged pool memory can be accessed by Windows. If Windows runs out of kernel memory, it can display error messages and crash. Kernel memory is essential to the correct operation of the system, and therefore you should monitor kernel memory carefully.

To correct this error

  1. Restart the Exchange Server computer at the earliest convenience.

  2. If this condition recurs, make sure that your system is tuned correctly and that all of the software and hardware on the system is up to date. This includes installing the latest versions of the following programs:

    • Windows operating system service pack

    • Exchange Server service pack

    • Hardware firmware and drivers

    • System BIOS updates

    • Updates for any third-party applications that are installed and running

  3. If software and hardware updates do not resolve this problem, disable all third-party software, restart the Exchange Server computer, and monitor kernel memory.

  4. Use Memory Pool Monitor (Poolmon.exe) to monitor the non-paged pool to make sure that it is not climbing above the threshold for the system.

  5. Use Process Explorer to view the absolute maximum levels that the system supports as defined in "Memory Management - Understanding Pool Resources" (

For more information about tuning Exchange Server correctly, see the following Microsoft Knowledge Base articles and white papers:

For more information about the nonpaged pool memory and related topics, see the following Knowledge Base articles:

For more information about Process Explorer, see "Memory Management - Understanding Pool Resources" (